Type of threads - How to identify threads

TYPE OF THREAD | 1

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W.TEESING.COM

S. L. ten Cate08-2015

TYPES OF THREAD

2 | TEESING

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© Teesing BV, Aug 2015. Versie 030815All technical and other data contained in this catalogue may be subject to change without notice.The contents of this document have been written with the greatest possible care. However, Teesing cannot guarantee the accuracy or completeness of the information provided in this brochure.

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BASICS OF THREAD

INDEX

TYPE OF THREAD | 3

1. BASICS OF THREAD1.1 Gender 4

1.2 Handedness 4

1.3 Design 4

1.4 Pitch / TPI 5

1.5 Diameter 5

1.6 Angle 5

1.7 Crest / root 5

2. MOST COMMON THREADS2.1 M - ISO thread (metric) 7

2.2 NPT - Pipe thread 8

2.3 G/R/Rp - Whitworth thread (BSPP/BSPT) 9

2.4 UNC/UNF - Unified National thread 10

2.5 Extra: Comparison sheet (M – BSPP – BSPT – NPT – UNC - UNF) 11-15

3. FREQUENTLY ASKED QUESTIONS3.1.1 How to identify thread types? 16

3.1.2 What does NPTF stand for: Female, Fine or fuel? 16

3.1.3 Which female threads are tapered/conical? 16

3.1.4 What is the difference between G-thread (BSPP) and R-thread (BSPT)? 16-18

3.1.5 Can I use an o-ring sealing with NPT thread? 18

3.1.6 Are NPT and BSP Pipe threads compatible? 19

3.1.7 What is screw/nut galling and how can it be avoided? 19

3.1.8 What kind of sealing method is recommended when mounting a PA/PVDF 19

fitting with male taperd thread into a metal counterpart?

3.1.9 What kind of a thread does a Jic-fitting have? 20

3.2 THREAD SEAL TYPES 20

Appendix: Conversion factor 21

Appendix: Other threads 22-23

4 | TEESING

Parallel Tapered

GENDEREvery matched pair of threads, external and internal, can be described as male and female. For example, a screw has male thread, while the matching hole has female thread.

HANDEDNESSThe helix of a thread can twist in two possible directions. Most threads are oriented so that the threaded item when seen from a point of view on the axis through the center of the helix, moves away from the viewer when it is turned in a clockwise direction, and moves towards the viewer when it is turned counter clockwise.

By common convention, right-handedness is the default handedness for screw threads. Therefore, most threaded parts and fasteners have right-handed threads.

1.1 1.4

1.2

1.5

1.6

1.7

1.3 DESIGNThe type of thread can be identified by the following characteristics.

1. BASICS OF THREAD

Internal Thread(Female)

Right-hand Left-hand

External thread(Male)


TYPE OF THREAD | 5

Flank angle

1° 47´Taper angle

1.4

1.5

1.6

1.7

1. BASICS OF THREAD

Pitch

Majordiameter

Pitch diameter

Minordiameter

Depth

Threads perInch = TPI

ANGLEThe flank angle is the angle between the flank of a screw thread and the perpendicular to the axis of the screw. Tapered threads have a taper angle. This is the angle between the taper and the centre axis of the pipe.

CREST/ROOTThe outer-most part of the thread is called crest, the inner-most part of the thread is called root.

PITCH/TPI:The pitch is the distance from the crest of one thread to the next in mm. TPI (Threads per inch) is used by inch thread.

DIAMETER:The major diameter is determined by the thread tips.The minor diameter is determined by the groove of the thread.The pitch diameter is the distance of two opposite flanks or the distance of the centreline of the profile.

6 | TEESING

M - ISO THREAD (METRIC)M Coarse Thread ISO 724 (DIN 13-1)M Fine Thread ISO 724 (DIN 13-2 to 11)

NPT - PIPE THREADNPT ANSI B1.20.1NPTF ANSI B1.20.3

G/R/RP - WHITWORTH THREAD (BSPP/BSPT)G = BSPP ISO 228 (DIN 259)R/Rp/Rc = BSPT ISO 7 (DIN 2999 replaced by EN10226)

UNC/UNF - UNIFIED NATIONAL THREADUNC ANSI B1.1UNF ASNI B1.1

EXTRA: COMPARISON SHEET (M – BSPP – BSPT – NPT – UNC - UNF)

2. MOST COMMON THREADS

2.12.1

2.2

2.3

2.5

2.4


TYPE OF THREAD | 7

M - ISO THREAD (METRIC)ISO Metric thread is a globally standardized thread. Compared to standard threads (coarse thread), a fine thread has a smaller pitch.

Coarse Thread Fine Threadpitch can be displayed or omitted after thread size pitch must be displayed after thread size

The flank angle is 60°.Female and Male thread are both parallel.

Thread size (mm)

Major diameter (mm)

Minor diameter (mm)

Pitch (mm) Thread size (mm)

Major diameter (mm)

Minor diameter (mm)

Pitch (mm)

M 3 2,98 2,459 0,5 M 3 x 0,35 2,981 2,621 0,35

M 4 3,978 3,242 0,7 M 4 x 0,5 3,978 3,242 0,5

M 5 4,976 4,134 0,8 M 5 x 0,5 4,98 4,459 0,5

M 6 5,974 4,917 1 M 6 x 0,75 5,978 5,188 0,75

M 8 7,974 6,917 1 M 8 x 0,75 7,978 7,188 0,75

M 10 9,968 8,376 1,5

M 10 x 0,75 9,978 9,188 0,75

M 10 x 1 9,974 8,917 1

M 10 x 1,25 9,972 8,647 1,25

M 12 11,97 10,106 1,75

M 12 x 1 11,97 10,917 1

M 12 x 1,25 11,97 10,647 1,25

M 12 x 1,5 11,97 10,376 1,5

M 16 15,96 13,835 2 M 16 x 1 15,97 14,917 1

M 16 x 1,5 15,97 14,376 1,5

M 20 19,96 17,294 2,5 M 20 x 1 19,97 18,917 1

M 20 x 1,5 19,97 18,376 1,5

M 20 x 2 19,96 17,835 2

M 24 23,95 20,752 3 M 24 x 1,0 23,97 22,917 1,0

M 24 x 1,5 23,97 22,376 1,5


2.1

8 | TEESING

NPT - PIPE THREAD The most common types of pipe thread are:• NPT - American Taper Pipe Thread = National Pipe Taper• NPTF - American Taper Pipe Thread for Dryseal joint without sealant compound = National Pipe Taper Fuel

NPT and NPTF appear to be identical. Both have the same pitch diameter at the top of the hole of the internal thread or end of the pipe on external threads and both have the same thread lengths or depths. However, there is a subtle difference in the root and crest diameters of the threads.

NPT / NPTFThread size Major Diameter (mm) TPI

1/16” – 27 NPT 7,938 27

1/8” – 27 NPT 10,287 27

1/4” – 18 NPT 13,716 18

3/8” – 18 NPT 17,145 18

1/2” – 14 NPT 21,336 14

3/4” – 14 NPT 26,670 14

1” – 11 ½ NPT 33,401 11,5

2” – 11 ½ NPT 60,325 11,5

The flank angle is 60°.Female and Male thread are both tapered with equal angles.

NPT threads are also sometimes referred to as:• MIP (Male Iron Pipe)• FIP (Female Iron Pipe)• IPT (Iron Pipe Thread)• FPT (Female Pipe Thread)• MPT (Male Pipe Thread)

Note that these references are somewhat casual, and might possibly be used in reference to NPS instead of NPT Thread. NPS thread –National Pipe Straight- is not interchangeable with NPT thread.


2.2


TYPE OF THREAD | 9

G/R/RP - WHITWORTH THREAD (BSPP/BSPT)The most common types of whitworth thread are:• BSPP (G) – British Standard Pipe Parallel • BSPT (R/Rp) – British Standard Tapered Pipe, for pipes and tapered thread. An appropriate sealing compound can be used in the thread to ensure a leak-proof joint.

BSPP (G)Thread size (inch) Major Diameter (mm) Minor Diameter (mm) TPI

G 1/16” 7,723 6,561 28

G 1/8” 9,728 8,566 28

G 1/4” 13,157 11,445 19

G 3/8” 16,662 14,950 19

G 1/2” 20,955 18,631 14

G 3/4” 26,441 24,117 14

G 1” 33,249 30,291 11

G 2” 59,614 56,656 11

BSPT (R/Rp)Male Thread size (inch)

Female Thread size (inch)

Major Diameter (mm)

Minor Female Diameter (mm)

TPI

R 1/16” Rp 1/16” 7,723 6,490 28

R 1/8” Rp 1/8” 9,728 8,495 28

R 1/4” Rp 1/4” 13,157 11,341 19

R 3/8” Rp 3/8” 16,662 14,846 19

R 1/2” Rp 1/2” 20,955 18,489 14

R 3/4” Rp 3/4” 26,441 23,975 14

R 1” Rp 1” 33,249 30,111 11

R 2” Rp 2” 59,614 56,476 11

The flank angle is 55°.BSPP: Female and Male thread are both parallel.BSPT: Female thread is parallel and male thread is tapered. - Female thread can also be tapered: Rc, but this is not common.

BSPP BSPT


2.3

10 | TEESING

UNC/UNF - UNIFIED NATIONAL THREADThe most common types of UN (Unified National) thread are:• UNC – Unified National Coarse Thread, comparable with the ISO metric thread.• UNF – Unified National Fine Thread. *Compared to standard threads (coarse thread), a fine thread has a smaller pitch.

Unified threads come in three different classes:1A (external) & 1B (internal): for applications where a liberal tolerance is required to permit easy

assembly even with slightly nicked threads.2A (external) & 2B (internal): most commonly used class for general applications3A (external) & 3B (internal): for applications where closeness of fit and/or accuracy of thread

elements are important.

UNC (2A)Nominal Diameter Major Diameter (mm) Minor Diameter (mm) TPI

1/4” x 20 UNC 6,322 4,978 20

5/16” x 18 UNC 7,907 6,401 18

3/8” x 16 UNC 9,491 7,798 16

7/16” x 14 UNC 11,076 9,144 14

1/2” x 13 UNC 12,661 10,592 13

5/8” x 11 UNC 15,834 13,386 11

3/4” x 10 UNC 19,004 16,307 10

7/8” x 9 UNC 22,176 19,177 9

1” x 8 UNC 25,349 21,971 8

2” x 4,5 UNC 50,726 44,679 4,5

UNF (2A)Nominal Diameter Major Diameter (mm) Minor Diameter (mm) TPI

1/4” x 28 UNF 6,325 5,360 28

5/16” x 24 UNF 7,910 6,782 24

3/8” x 24 UNF 9,497 8,382 24

7/16” x 20 UNF 11,079 9,728 20

1/2” x 20 UNF 12,667 11,328 20

5/8” x 18 UNF 15,839 14,351 18

3/4” x 16 UNF 19,012 17,323 16

7/8” x 14 UNF 22,184 20,269 14

1” x 12 UNF 25,354 23,114 12

The flank angle is 60°.Female and Male thread are both parallel.


2.4


TYPE OF THREAD | 11

EXTRA: COMPARISON SHEET (M – BSPP – BSPT – NPT – UNC - UNF)

UNC (2A)Metric:Standard/Fine

Inch:BSPP (G) BSPT (R) NPT UNC/UNF

Type Parallel Parallel Tapered Tapered Parallel

Flank angle 60° 55° 55° 60° 60°

Thread angle 0° 0° 1°47’ 1°47’ 0°

Seal location O-ring/ Gasket/Cone

O-ring/ Gasket/Cone

On threads On threads O-ring/ Gasket/Cone

Major Diameter (mm):BSPP (G) BSPT (R/Rp) NPT UNC UNF

1/16” 7,723 7,723 7,938

1/8” 9,728 9,728 10,287

1/4” 13,157 13,157 13,716 6,322 6,325

3/8” 16,662 16,662 17,145 9,491 9,497

1/2” 20,955 20,955 21,336 12,661 12,667

3/4” 26,441 26,441 26,670 19,004 19,012

1” 33,249 33,249 33,401 25,349 25,354

2” 59,614 59,614 60,325 50,726 -

Minor Diameter (mm):BSPP (G) BSPT (R/Rp) UNC UNF

1/16” 6,561 6,490

1/8” 8,566 8,495

1/4” 11,445 11,341 4,978 5,360

3/8” 14,950 14,846 7,798 8,382

1/2” 18,631 18,489 10,592 11,328

3/4” 24,117 23,975 16,307 17,323

1” 30,291 30,111 21,971 23,114

2” 56,656 56,476 44,679 -

TPI (Treads per inch):BSPP (G) BSPT (R/Rp) NPT UNC UNF

1/16” 28 28 27

1/8” 28 28 27

1/4” 19 19 18 20 28

3/8” 19 19 18 16 24

1/2” 14 14 14 13 20

3/4” 14 14 14 10 16

1” 11 11 11,5 8 12

2” 11 11 11,5 4,5 -


2.5

12 | TEESING

Male thread

D (mm) pitch (mm) TPI (threads per inch)

BSP (BSPP & BSPT)

Metric fine NPT UN/JIC/SAE (Thread class 2)

9,73 28 1/8

9,97 1 M10x1

10,29 27 1/8

11,11 20 7/16-20 UNF

11,97 1,5 M12x1,5

12,70 20 1/2-20 UNF

13,16 19 1/4

13,72 18 1/4

13,97 1,5 M14x1,5

14,29 18 9/16-18 UNF

15,88 18 5/8-18 UNF

15,97 1,5 M16x1,5

16,66 19 3/8

17,15 18 3/8

17,46 16 11/16-16 UN

17,97 1,5 M18x1,5

19,05 16 3/4-16 UNF

19,97 1,5 M20x1,5

20,64 16 13/16-16 UNF

20,96 14 1/2

21,34 14 1/2

21,97 1,5 M22x1,5

22,23 14 7/8-14 UNF

23,97 1,5 M24x1,5

25,40 12 1-12 UN

25,97 1,5 M26x1,5

26,44 14 3/4

26,67 14 3/4

26,96 2 M27x2

26,99 12 1 1/16-12 UN

26,99 16 1 1/16-16 UN



TYPE OF THREAD | 13

Male thread


BSP (BSPP & BSPT)


29,96 1,5 M30x1,5

29,96 2 M30x2

30,16 12 1 3/16-12 UN

32,96 2 M33x2

33,25 11 1

33,34 12 1 5/16-12 UN

33,40 11,5 1

35,96 2 M36x2

36,51 12 1 7/16-12 UN

37,96 1,5 M38x1,5

41,28 12 1 5/8-12 UN

41,91 11 1 1/4

41,96 1,5 M42x1,5

41,96 2 M42x2

42,16 11,5 1 1/4

42,86 12 1 11/16-12 UN

44,96 1,5 M45x1,5

44,96 2 M45x2

47,63 12 1 7/8-12 UN

47,80 11 1 1/2

47,96 2 M48x2

48,26 11,5 1 1/2

50,80 12 2-12 UN

51,96 1,5 M52x1,5

51,96 2 M52x2

59,61 11 2

60,33 11,5 2

63,50 12 2 1/2-12 UN

64,96 2 M65x2


14 | TEESING

Female thread


BSP (BSPP & BSPT)


8,54 27 1/8

8,57 28 1/8

8,92 1 M10x1

9,73 20 7/16-20 UNF

10,38 1,5 M12x1,5

11,07 18 1/4

11,33 20 1/2-20 UNF

11,45 19 1/4

12,38 1,5 M14x1,5

12,75 18 9/16-18 UNF

14,35 18 5/8-18 UNF

14,38 1,5 M16x1,5

14,49 18 3/8

14,95 19 3/8

15,75 16 11/16-16 UN

16,38 1,5 M18x1,5

17,32 16 3/4-16 UNF

17,90 14 1/2

18,38 1,5 M20x1,5

18,63 14 1/2

18,92 16 13/16-16 UN

20,27 14 7/8-14 UNF

20,38 1,5 M22x1,5

22,38 1,5 M24x1,5

23,11 12 1-12 UNF

23,21 14 3/4

24,12 14 3/4

24,38 1,5 M26x1,5

24,69 12 1 1/16-12 UN

24,84 2 M27x2

25,27 16 1 1/16-16 UN



TYPE OF THREAD | 15

Female thread


BSP (BSPP & BSPT)


27,84 2 M30x2

27,86 12 1 3/16-12 UN

28,38 1,5 M30x1,5

29,15 11,5 1

30,29 11 1

30,84 2 M33x2

31,04 12 1 5/16-12 UN

33,84 2 M36x2

34,21 12 1 7/16-12 UN

36,38 1,5 M38x1,5

37,87 11,5 1 1/4

38,95 11 1 1/4

38,99 12 1 5/8-12 UN

39,84 2 M42x2

40,38 1,5 M42x1,5

40,56 12 1 11/16-12 UN

42,84 2 M45x2

43,38 1,5 M45x1,5

43,49 11,5 1 1/2

44,85 11 1 1/2

45,34 12 1 7/8-12 UN

45,84 2 M48x2

48,51 12 2-12 UN

49,84 2 M52x2

50,38 1,5 M52x1,5

56,66 11 2

57,63 11,5 2

61,21 12 2 1/2-12 UN

62,84 2 M65x2


16 | TEESING

WHAT IS THE DIFFERENCE BETWEEN G-THREAD (BSPP) AND R-THREAD (BSPT)?BSPT thread is tapered when we speak about male thread (R), but the female thread can be tapered (Rc) or parallel (Rp). BSPP thread is parallel, male and female (G).

What is the difference then between female parallel Rp-thread and female parallel G-thread?G-threads have a parallel shape in accordance with the DIN-EN-ISO 228-1 standard. Rp-threads have a parallel shape in accordance with the ISO 7-1 and DIN-EN 10226-1 standard. In the case of a thread of size 1/8”, for example, the threads are specified as G1/8 or R1/8. Male G-threads (parallel) can only be screwed into female G-threads. Male R-threads (tapered) can be screwed into female G or R-threads.The following table shows the internal minimum thread diameter, with the upper deviation.

3. INFORMATION

3.1 FREQUENTLY ASKED QUESTIONS

3.1.2

3.1.1

30˚Thread

O.D.

HOW TO IDENTIFY THREAD TYPES?1. Determine if the thread is male or female (visual inspection)?2. Determine if the thread is tapered or straight/parallel (visual inspection)? • Check: Measure the thread with a calliper at the beginning and the end,

if it is the same value the thread is straight/parallel.3. Measure the thread diameter (male: major diameter, female: minor diameter). • The diameter measurement obtained in this step may not be exactly the same as the listed nominal size

for the given thread. The main reason for this variation is industry or manufacturing tolerances.4. Determine the thread pitch. • Easiest with the use of a pitch gauge.5. Identify the end connection. • Most common angles: 30°, 37° and 45°.

Thread identification exampleAccording to the mentioned method:1. The fitting is visably male.2. The thread is visably straight.3. The meassured diameter is 26,4 mm (this can be easily converted: inches decimal x 25,4 = mm).4. Threads per inch (TPI): 14 • When you are not sure, you can search the threading table for a matching diameter and find the possible thread pitches. (For example UNC and UNF have ‘the same diameter’ but the TPI is different 20 or 28).5. Not applicable.

Result: G3/4 male thread.

WHAT DOES NPTF STAND FOR: FEMALE, FINE OR FUEL?NPTF stands for National Pipe Taper Fuel. This could be male or female. NPTF is designed to provide a more leak-free seal without the use of teflon tape or other sealant compound. A common mistake is to assume that NPTF stands for NPT female or NPT fine. NPT fine does not exist.

WHICH FEMALE THREADS ARE TAPERED/CONICAL?Most common used tapered internal threads:• NPT• BSPT: Rc

3.1.3

3.1.4


TYPE OF THREAD | 17

3. INFORMATION

ø TPI ø Drill - øB Nut Thread minor øMin

Nut Thread minor øMax

G 1/16 28 7.723 6.80 6.516 6.843

G 1/8 28 9.728 8.80 8.566 8.848

G 1/4 19 13.157 11.80 11.445 11.890

G 3/8 19 16.662 15.25 14.950 15.395

G 1/2 14 20.955 19.00 18.631 19.172

G 5/8 14 22.911 21.00 20.587 21.128

G 3/4 14 26.441 24.50 24.117 24.658

G 7/8 14 30.201 28.25 27.877 28.418

G 1 11 33.249 30.75 30.291 30.931

G 1.1/8 11 37.897 35.50 34.939 35.579

G 1.1/4 11 41.910 39.50 38.952 39.592

G 1.3/8 11 44.320 42.00 41.365 42.005

G 1.1/2 11 47.803 45.25 44.845 45.485

G 1.3/4 11 53.746 51.10 50.788 51.428

G 2 11 59.614 57.00 56.656 57.296

G 2.1/4 11 65.710 63.10 62.752 63.392

G 2.1/2 11 75.184 73.00 72.226 72.866

G 2.3/4 11 81.534 79.00 78.576 79.216

G 3 11 87.884 85.50 84.926 85.566

G 3.1/2 11 100.330 98.00 97.327 98.012

G 4 11 113.030 110.50 110.072 110.712

G - WITHWORTH PIPE THREAD

ø TPI ø Drill - øB Nut Thread minor øMin

Nut Thread minor øMax

Rp 1/16 28 7.723 6.55 6.490 6.632

Rp 1/8 28 9.728 8.60 8.495 8.637

Rp 1/4 19 13.157 11.50 11.341 11.549

Rp 3/8 19 16.662 15.00 14.846 15.054

Rp 1/2 14 20.955 18.50 18.489 18.773

Rp 3/4 14 29.441 24.00 23.975 24.259

Rp 1 11 33.249 30.25 30.111 30.471

Rp 1.1/4 11 41.910 39.00 38.772 39.132

Rp 1.1/2 11 47.803 45.00 44.665 45.025

Rp 2 11 59.614 56.50 56.476 56.836

Rp 2.1/2 11 75.184 72.25 72.083 72.443

Rp 3 11 87.884 85.00 84.783 85.143

Rp 4 11 113.030 110.00 109.860 110.289

RP - WITHWORTH PIPE THREAD

18 | TEESING

3. INFORMATION

3.1.6

3.1.5

The tolerances on the pitch diameter of the internal G-threads correspond to the ‘positive’ deviation of the diameter tolerances in ISO 7-1, with the exception of those for thread sizes 1/16, 1/8, 1/4 and 3/8, for which slightly higher values are specified.

INTERNAL G-THREAD RP-THREAD

Designation of thread

Number of threads in25.4 mm

Pitch Tolerance on pitch diameter Thread size Equivalent diametral tolerance on parallel internal threads

mm

Internal thread lower deviation

Internal thread Upper deviation

1/16 28 0.907 0 +0.107 1/16 +/-0.071

1/8 28 0.907 0 +0.107 1/8 +/-0.071

1/4 19 1.337 0 +0.125 1/4 +/-0.104

3/8 19 1.337 0 +0.125 3/8 +/-0.104

1/2 14 1.814 0 +0.142 1/2 +/-0.142

5/8 14 1.814 0 +0.142

3/4 14 1.814 0 +0.142 3/4 +/-0.142

7/8 14 1.814 0 +0.142

1 11 2.309 0 +0.180 1 +/-0.180

1 1/8 11 2.309 0 +0.180

1 1/4 11 2.309 0 +0.180 1 1/4 +/-0.180

1 1/2 11 2.309 0 +0.180 1 1/2 +/-0.180

1 3/4 11 2.309 0 +0.180

2 11 2.309 0 +0.180 2 +/-0.180

The combination of an external parallel thread G, tolerance A or B in accordance with DIN-EN-ISO228-1 with an internal parallel thread Rp in accordance with ISO 7-1, needs special consideration.When it is necessary to have this combination, the positive or negative tolerance of the internalthread in accordance with ISO 7-1 shall be considered in the relevant product standards, whereexternal parallel thread G are used.

Never try to mate a BSP fitting with an NPT (or NPS) fitting if the pressure holding capability is at all critical.

CAN I USE AN O-RING SEALING WITH NPT THREAD?Sealing NPT thread with an o-ring is impossible. NPT thread is tapered thread and should screw in only partway. Therefore, the sealing itself is realized directly on the thread, with PTFE tape or a liquid sealant.


TYPE OF THREAD | 19

3. INFORMATION

3.1.6

3.1.7

3.1.8

ARE NPT AND BSP PIPE THREADS COMPATIBLE?While NPT threads are common in the United States, BSP threads are widely used in many other countries.NPT/NPS and BSP threads are not compatible due to the differences in their thread forms, and not just the fact that most diametrical sizes have a different pitch. NPT/NPS threads have a 60° included angle and have flattened peaks and valleys; BSP threads have a 55° included angle and have rounded peaks and valleys.(Sometimes ½” and ¾” NPT and BSP threads are combined, because they are very close in design, they have the same pitch).

Never try to mate a BSP fitting with an NPT (or NPS) fitting if the pressure holding capability is at all critical.

Pipe Size Pitch (Threads/Inch)

NPT/NPS BSP

1/16" 27 ---

1/8" 27 28

1/4" 18 19

3/8" 18 19

1/2" 14 14

5/8" --- 14

3/4" 14 14

1" 11 1/2 11

WHAT IS SCREW/NUT GALLING AND HOW CAN IT BE AVOIDED?Galling occurs when two like metals rub against each other. As the metals heat up from friction, the molecules of each bind together, eventually causing failure as the surfaces weld together. The higher the speed and the higher the pressure, the more likely this is to occur. Often different kind of fasteners, such as those made of stainless steel, aluminium and titanium are most likely to be subject to galling when tightened. Galling can be avoided by good lubrication, by using PTFE tape and by using brass or plastic nuts instead of for example stainless steel nuts. Metal-to-metal contacts are appropriate for low duty cycles or when good lubrication can be supplied, otherwise, stainless steel nuts running on stainless steel screws should be avoided.

WHAT KIND OF SEALING METHOD IS RECOMMENDED WHEN MOUNTING A PA/PVDF FITTING WITH MALE TAPERED THREAD INTO A METAL COUNTERPART?This combination of materials is not ideal and therefore not recommended. However, when this combination is prescribed, our advice is to use PTFE-tape. There is a possibility that a leaktight connection can be achieved without PTFE-tape, but there is a greater chance of damaging the thread on the PA/PVDF coupling. Damaged thread increases the risk of leaks and after removal the fitting must be replaced.

20 | TEESING

Parallel and tapered threads require different sealing solutions.

When the female thread and the male thread are both parallel an o-ring or bonded seal is often used. O-rings are one of the most common seals, because they are inexpensive, easy to make, reliable and have simple mounting requirements. When the male thread is tapered an o-ring seal can’t be used, because the thread can only be screwed in only partially. At Teesing we use PTFE tape or Loctite. Without an additional sealant all tapered threads leak! The sealant reduces the potential for galling of the threads.

THREAD SEAL TYPES

3. INFORMATION

3.2

3.1.9 WHAT KIND OF THREAD DOES A JIC-FITTING HAVE?A JIC-fitting -Joint Industry Council- is a type of flare fitting machined with a 37-degree flare seating surface and UNF thread. The flare fittings seal with metal to metal contact between the flared nose of the fitting and the flared tube face in the female connection.

Fitting size (JIC) UNF thread

D02 5/16x24

D03 3/8x24

D04 7/16x20

D05 1/2x20

D06 9/16x18

D07 5/8x18

D08 3/4x16

D10 7/8x14

D12 1 1/16x12

D16 1 5/16x12

D20 1 5/8x12

D24 1 7/8x12


TYPE OF THREAD | 21

O-rings Bonded seals

APPENDIX: CONVERSION FACTOR

Length 1 inch = 0,0254 m

1 foot = 0,3048 m

Temperature 1 Fahrenheit = 5/9(°F-32) °C

Force 1 kgf = 9,81 N

Pressure 1 kgf/cm² = 0,0981•106 Pa

1 atm = 0,981 bar

1 lb/in² (psi) = 0,0689 bar

1 cal = 4,187 J

1 kWh = 3,6•106 J

1 kcal/h = 1,163 W

1 pk = 745,5 W

Inches Inches decimal Millimeters

1/16” 0,0625 1,588

1/8” 0,125 3,175

¼” 0,25 6,350

3/8” 0,375 9,525

½” 0,5 12,700

¾” 0,75 19,050

1” 1 25,400

2” 2 50,800

3. INFORMATION3. INFORMATION

22 | TEESING

APPENDIX: OTHER THREADS

Pipe thread

NPSC – NPSF – NPSL – NPSM ANSI B1.20.1-1983

Whitworth thread UN (Unified National) thread

BSF Fine thread BS 84 UNEF Extra Fine thread ANSI B1.1W = BSW Coarse thread BS 84 UNR ANSI B1.1 UNS ANSI B1.1

Trapezoidal thread

Tr DIN 103

3. INFORMATION3. INFORMATION 3. INFORMATION



TYPE OF THREAD | 23

APPENDIX: OTHER THREADS

Knuckle thread Buttress threadRd DIN 405 / DIN 20400 S DIN 513 / DIN 514

Cycle thread Edison threadFg DIN 79012 E DIN 40400

3. INFORMATION

24 | TEESING

WWW.TEESING.COM

TEESING B.V.Verrijn Stuartlaan 40

2288 EL Rijswijk

The Netherlands

Tel +31 70 413 07 00

Fax +31 70 413 07 30

[email protected]

www.teesing.com

CHINA OFFICEHong Kong Macau Center

Suite 418

4Th Floor, Office Tower

2 Chao Yang Men Bei Da Jie

100028 Beijing, China

Tel +86 10 659 590 74

Fax +86 10 650 142 48

[email protected]

www.teesing.com.cn

USA OFFICE10 Millpond Drive Unit 7

Lafayette, NJ 07848

United States of America

Tel +1 973 383 0691

Fax +1 973 383 4672

[email protected]

www.teesing.com

TAIWAN OFFICE4F.-15, No.36, Taiyuan St.

Zhubei City

Hsinchu County 302

Taiwan

Tel +886 3 560 05 60

Fax +886 3 560 05 25

[email protected]

www.teesing.tw

ASPRO TIS (BEIJING) CO. LTD.Xi Tuo Cun, Ma Chi Kou Zhen

Chang Ping District

Beijing 102206

China

Tel +86 10 807 221 65

[email protected]

www.aspro-tis.com.cn

Contact our sales engineers to receive detailed product information. We recommend to visit our website for regularly updated product information.

Engineering

Type of threads - How to identify threads